From: "Reshetova, Elena" <elena.reshetova@intel.com>
To: Mike Snitzer <snitzer@redhat.com>
Cc: Alasdair G Kergon <agk@redhat.com>,
"dm-devel@redhat.com" <dm-devel@redhat.com>,
"keescook@chromium.org" <keescook@chromium.org>,
"peterz@infradead.org" <peterz@infradead.org>,
"shli@kernel.org" <shli@kernel.org>,
"koverstreet@google.com" <koverstreet@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-raid@vger.kernel.org" <linux-raid@vger.kernel.org>,
"linux-bcache@vger.kernel.org" <linux-bcache@vger.kernel.org>,
"ejt@redhat.comg" <ejt@redhat.comg>,
"kent.overstreet@gmail.com" <kent.overstreet@gmail.com>,
Zdenek Kabelac <zkabelac@redhat.com>
Subject: RE: [dm-devel] [PATCH 3/4] dm: convert dm_dev_internal.count from atomic_t to refcount_t
Date: Tue, 28 Nov 2017 10:07:08 +0000 [thread overview]
Message-ID: <2236FBA76BA1254E88B949DDB74E612B802C3EDA@IRSMSX102.ger.corp.intel.com> (raw)
In-Reply-To: <CAMM=eLfrnQqBH06pPnNKfmeF=AjScAxjR1WD7Ur9NAEY=4Sxog@mail.gmail.com>
[-- Attachment #1: Type: text/plain, Size: 2420 bytes --]
> On Fri, Nov 24, 2017 at 2:36 AM, Reshetova, Elena
> <elena.reshetova@intel.com> wrote:
> >> On Fri, Oct 20, 2017 at 10:37:38AM +0300, Elena Reshetova wrote:
> >> > } else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) {
> >> > r = upgrade_mode(dd, mode, t->md);
> >> > if (r)
> >> > return r;
> >> > + refcount_inc(&dd->count);
> >> > }
> >>
> >> Missing here:
> >>
> >> else
> >> refcount_inc(&dd->count);
> >>
> >> ?
> >
> > Oh, yes, thanks for catching this! I think this got unnoticed so far and patch was
> merged, so I am going to send a followup patch now.
>
> I pushed this fix and will send to Linus next week:
> https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-
> dm.git/commit/?h=dm-4.15&id=d908af82d06cc420f9581c97c6db941cb87e4434
I guess you mean this commit:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=c2318d07ead871f058dda62e942ed7b6b1c1cfcf
Unfortunately it is not correct:
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 88130b5..f6d32ee 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -451,15 +451,15 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
return r;
}
- refcount_set(&dd->count, 1);
+ refcount_set(&dd->count, 0);
list_add(&dd->list, &t->devices);
} else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) {
r = upgrade_mode(dd, mode, t->md);
if (r)
return r;
- refcount_inc(&dd->count);
}
+ refcount_inc(&dd->count);
Problem will be here if you hit this refcount_inc() after the refcount_set(&dd->count, 0) earlier.
refcount_inc() does not increment on zero value *ever* for security reasons and instead people
should initialize refcounters to 1 always and do increments from there if needed.
This was the reason for the initial change I did, my mistake was just to forget to increment it also
in case condition (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) fails.
I have issues with my intel smpt server for sending patches (I will get it fixed tomorrow from internal network),
so I am attaching the patch I did end of last week to this thread instead (or alternatively can properly send it tomorrow after fix).
Sorry for the delay!
Best Regards,
Elena.
[-- Attachment #2: 0001-dm-fix-the-missing-increment-for-dm_dev_internal.cou.patch --]
[-- Type: application/octet-stream, Size: 1210 bytes --]
From 715977ac0090cf3ee8ddc339c292434e20a9c93d Mon Sep 17 00:00:00 2001
From: Elena Reshetova <elena.reshetova@intel.com>
Date: Fri, 24 Nov 2017 10:02:48 +0200
Subject: [PATCH] dm: fix the missing increment for dm_dev_internal.count
The commit 2a0b4682e09d76466f7b8f5e347ae2ff02f033af
mistakenly forgotten one case where refcount must be
incremented. Fix this.
Reported-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Elena Reshetova <elena.reshetova@intel.com>
---
drivers/md/dm-table.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 88130b5..eb0ba2a 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -453,14 +453,19 @@ int dm_get_device(struct dm_target *ti, const char *path, fmode_t mode,
refcount_set(&dd->count, 1);
list_add(&dd->list, &t->devices);
+ *result = dd->dm_dev;
+ return 0;
+
+ }
- } else if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) {
+ if (dd->dm_dev->mode != (mode | dd->dm_dev->mode)) {
r = upgrade_mode(dd, mode, t->md);
if (r)
return r;
- refcount_inc(&dd->count);
}
+ refcount_inc(&dd->count);
+
*result = dd->dm_dev;
return 0;
}
--
2.7.4
next prev parent reply other threads:[~2017-11-28 10:07 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-20 7:37 [PATCH 0/4] dm and bcache refcount conversions Elena Reshetova
2017-10-20 7:37 ` [PATCH 1/4] bcache: convert cached_dev.count from atomic_t to refcount_t Elena Reshetova
2017-10-20 18:39 ` Michael Lyle
2017-10-23 6:45 ` Reshetova, Elena
2017-10-20 7:37 ` [PATCH 2/4] dm cache: convert dm_cache_metadata.ref_count " Elena Reshetova
2017-10-20 7:37 ` [PATCH 3/4] dm: convert dm_dev_internal.count " Elena Reshetova
2017-11-23 15:49 ` [dm-devel] " Alasdair G Kergon
2017-11-24 7:36 ` Reshetova, Elena
2017-11-25 5:56 ` Mike Snitzer
2017-11-28 10:07 ` Reshetova, Elena [this message]
2017-11-28 19:02 ` Mike Snitzer
2017-11-29 8:05 ` Reshetova, Elena
2017-10-20 7:37 ` [PATCH 4/4] dm: convert table_device.count " Elena Reshetova
2017-11-23 15:19 ` Zdenek Kabelac
2017-11-24 8:29 ` Reshetova, Elena
2017-11-24 14:04 ` Alasdair G Kergon
2017-11-24 14:44 ` Reshetova, Elena
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